(a) Field of the Invention
This invention relates to thermosetting resin compositions that exhibit excellent heat resistance properties and are useful as adhesive films, laminating materials, and molding materials, and processes for preparing the same.
(b) Description of the Prior Art
Polyimide resins have conventionally been used widely in the industry due to their excellent heat resistance, electrical insulating properties and chemical resistance properties.
Among polyimide resins, condensation polyimide resins, which are prepared via polyamic acids by reacting a tetracarboxylic dianhydride and a diamine in a polyimide resin, are among the many resins that exhibit excellent properties. They are however accompanied by disadvantages such as high softening points and poor processabilities. Although a thermoplastic polyether imide that has improved processability at the sacrifice of some heat resistance ("Ultem", trade mark; product of General Electric Company) has been known, its heat resistance and chemical resistance are less than satisfactory .
On the other hand, addition-type polyimide resins prepared by polymerizing bismaleimide compounds exhibit excellent thermal properties but are inferior in mechanical strength. It is therefore impossible to form them into films by casting.